A Long-Term Evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. LTE systems also provide seamless integration to older wireless network, such as GSM, CDMA and Universal Mobile Telecommunication System (UMTS). In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of base stations, such as evolved Node-B's (eNBs) communicating with a plurality of mobile stations referred as user equipment (UEs). The dual connectivity (DC) UE is introduced to enhance bandwidth and flexibility use of the network. A UE with dual connectivity has more than one transceivers corresponding to more than one MAC entities. The multiple MAC entities can be configured to communicate with multiple eNBs simultaneously. With improved efficiency and flexibility, improvements for various functional tasks are desired. Two of such areas are buffer status report and logic group prioritization.
A Buffer status report (BSR) is sent from the UE to the serving eNB to provide information about the amount of pending data in the uplink buffer of the UE. The buffer status, along with other information, such as priorities allocated to different logical channels, is useful for the uplink scheduling process to determine which UEs or logical channels should be granted radio resources at a given time. The UE communicates the BSR to the scheduler in the base station so that the base station has sufficient information about the data waiting in the UE for UL transmission. The base station can allocate appropriate UL resource for the UE in a timely manner. Traditionally, the UE reports the buffer status to only one base station, which is its serving base station. This method encounters problem with the use of dual connectivity.
The logical channel prioritization (LCP) is required to make sure that all UE serves the uplink logical channels in a predefined sequence. LCP is performed when a new transmission is prepared. In the current system, where only one MAC entity for each UE, the LCP is performed at the UE level, taking into account all data buffered. With the dual connectivity for the UE, each MAC entity has its corresponding set of logical channel group (LCP). Different procedures are desired to improve the performance for LCP in a dual connectivity system.
Improvements and enhancements are required for UE BSR and LCP procedures to communicate and manage multiple schedulers from different base stations.